This application pertains generally to the art of fasteners and, more particularly, to fasteners for mounting a member to a support. The invention is particularly applicable for use in mounting electrical outlet boxes to bar hangers and will be described with reference thereto. However, it will be appreciated that the invention has broader aspects and may be used for mounting other members to supports.
Electrical outlet boxes are commonly clamped to bar hangers secured between joists or studs in a building. The bar hangers normally comprise telescoped channels so that the length of the bar hanger can be adjusted to fit between studs or joists of varied spacing. The clamping device for clamping an outlet box to the bar hanger and for clamping the hanger channels against movement relative to one another is normally assembled with the bar hanger at the factory. The most popular type of clamping device is one which does not have to be disassembled from the bar hanger by a workman in order to mount the outlet box. The clamping device is simply loosened so that the outlet box can be positioned on it, and the clamping device is then tightened to securely clamp the outlet box to the bar hanger.
One clamping device of the type described is disclosed in U.S. Pat. No. 2,295,333 issued Sept. 8, 1942, to Clark, and U.S. Pat. No. 3,080,084 issued Mar. 5, 1963, to Appleton. In clamping devices of this type, the outlet box must be tilted and moved sideways in order to locate the outlet box hole between the clamp and hanger. This means that the clamp must be very loose so that a workman must rotate the screw a relatively large number of turns to loosen the clamp and then tighten it. Also in these devices, care must be taken that the periphery of the outlet box hole remains in contact with alignment shoulders on the clamp so that the box will be clamped on both sides of the hole. When mounting outlet boxes with the opening facing horizontally, the box must be held with one hand against the clamp for proper positioning while the screw is tightened.
U.S. Pat. No. 2,824,167 issued Feb. 18, 1958, to Bauer, and U.S. Pat. No. 3,104,087 issued Sept. 17, 1963, to Budnick disclose outlet box clamping devices having legs which cooperate with cammed surfaces so that the legs flare outwardly to engage the box when the screw is tightened. In these devices, the outlet box must be held in position with one hand while the screw is tightened.
U.S. Pat. No. 3,214,126 issued Oct. 26, 1965, to Roos is of general interest for another type of outlet box clamping device. It is not clear how the clamping device in Roos is assembled to the outlet box.
U.S. Pat. No. 2,732,162 issued Jan. 24, 1956, to McKinley and U.S. Pat. No. 2,963,253 issued Dec. 6, 1960, to Maier et al disclose outlet box clamping devices which include spring clips. In the McKinley and Maier devices, a hole in an outlet box is aligned with a clamping device having spring legs which bend inwardly due to engagement of the hole periphery with such legs as the box is pushed toward the bar hanger. When that portion of the outlet box having the hole therein is positioned between the bar hanger and spring legs, such legs spring outwardly and a screw is then tightened to firmly clamp the outlet box between the bar hanger and spring legs. In the McKinley device, there is nothing to space the terminal ends of the spring legs from the facing surface of the bar hanger. Therefore, when the outlet box is pushed onto the clamping device, the terminal ends of the spring legs would abut the bar hanger and make it impossible for the outlet box wall to be positioned between the bar hanger and terminal end of the spring legs. The only way the outlet box could be installed would be by pulling on the clamping device while pushing on the outlet box and this would require the use of both hands. In the Maier device, there are spacer legs which engage the bar hanger for maintaining the terminal ends of the spring legs spaced from the bar hanger a distance greater than the thickness of the outlet box wall through which the hole is formed. Such spacer legs are scored so they can be deformed by tightening of the screw. The Maier device requires considerable material because the spacer legs are completely separate from the spring legs. In addition, the shape of the Maier clamping device, and the separate spacer legs make it somewhat difficult to form the device. There are some confusing disclosures in the Maier patent but correction of most of that confusion is believed to be generally obvious. For example, beginning in line 53 of column 3, there is a description of how the clamping device is assembled. As this description proceeds on over to column 4, it is explained that the screw is firmly tightened and the tips of the spacer legs deform to securely lock the telescoped bar hanger sections together, and to securely tighten the clamping device on the bar hanger. It is then stated that the outlet box is snapped into place. However, if one attempted to mount an outlet box in this manner, it would not be possible because the generally U-shaped mounting portion of the Maier device engages the spring legs so they could not yieldably deform inwardly as the box was pushed into place. In addition, there would be insufficient space between the terminal ends of the spring legs and the bar hanger to receive the wall of the outlet box through which the hole is formed. With the shape of a spring clip as shown in FIGS. 6 and 7 of the Maier patent, and as described in the specification, it would not be possible for the terminal ends of the spring legs to snap outwardly in the manner broadly suggested. This is because detents 37 are shown extending upwardly above the terminal ends of the spring clip which engage the bottom surface of the outlet box wall through which the hole is formed. Holes in shown and boxes are circular, and with the cup-like spring clip shownand described by Maier, detents 37 would engage the periphery of the hole even if the hole were above the terminal ends of the spring clip so outward snapping of the spring legs would not occur. It is believed that detents 37 of Maier would have to be bent inwardly from the terminal ends of the spring legs.